We plan to investigate the biochemical basis of information transfer across membranes and the role of such processes in development by analyzing the cAMP receptor which participates in the aggregation phase of the Dictyostelium discoideum life cycle. We will determine other membrane proteins which are physically or functionally associated with the receptor by (a) covalent attachment of radioactive labels to the receptor followed by cross linking of membrane proteins, (b) assays for cAMP-regulated enzymatic or binding activities in membranes and (c) similar studies with aggregation-defective mutant strains. We will also analyze the properties of a purified receptor protein to probe for the mechanism of its cAMP-induced activation of other membrane-associated functions. We will attempt to determine the role of cell contacts in regulation of receptor synthesis by using various means of interfering with the normal cell contact formation. We will also survey the total numbers of cAMP binding proteins during the life cycle to search for a possible second messenger role of cAMP in addition to its first messenger role in aggregation.